I would use a 51ohm resistor (E24 value), and some protection parts around it.
Then measure with 1.1volt Aref enabled in setup().
That will give you stable readings, independent of the Arduino's 5volt supply.
And over-current protection to 100mA, and more.
Just a random 4-20mA page with diagram in post#10.
That will also reduce voltdrop in the circuit (1volt instead of 5volt),
so your sensor supply can be lower.
Leo..